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Warning for Green and Black Tea Drinks!

Warning for Green and Black Tea Drinks!

Green Tea is a very popular drink not only in Asian countries but throughout the world.  In western nations, black tea is probably even more popular.

Green tea itself has many potential health benefits including promoting weight loss as well as beneficial effects on glucose tolerance (potentially beneficial for people with diabetes).  Both green, as well as black teas, are rich in polyphenols which are antioxidants.

Despite the many potential health benefits of both green and black teas, a recent study suggests that there may be one important adverse health-related effect related to tea consumption.

Folic Acid:

Folic acid is an important vitamin for several reasons.  Deficiencies of folic acid have been linked to the following conditions:

  • cardiovascular disease
  • growth retardation
  • megaloblastic anemia
  • neural tube defects (in children born from mother’s who have deficiency during pregnancy)
  • depression
  • increased levels of homocysteine

A recent study published in the journal, Biopharmaceutics & Drug disposition (Alemdaroglu et al, 2008), suggests that drinking either green or black tea may actually lower the bioavailability of folic acid.

Study Results:

At the 0.4 mg folic acid dose, green and black tea reduced the mean C(max) of serum folate by 39.2% and 38.6%

Study conclusion:

The present results suggest an in vivo interaction between tea and folic acid with even low concentrations of green and black tea extracts yielding decreased bioavailabilities of folic acid.

Important Implications:

  • Pregnant women may want to eliminate or at least restrict their consumption of both green/black tea.  Lower folic acid bioavailability is a potential risk for neural tube defects.
  • For those who do consume green/black teas, you will want to ensure that you don’t take your vitamins (containing folic acid) with tea.

Update 2019:

A new research study published in the journal of Epidemiology concluded:

Considering the negative associations of caffeine and tannin levels with serum folate levels, pregnant women should consume caffeinated beverages, such as coffee and green/oolong teas, with caution.


  1. Alemdaroglu NC, Dietz U, Wolffram S, Spahn-Langguth H, Langguth P. Influence of green and black tea on folic acid pharmacokinetics in healthy volunteers: potential risk of diminished folic acid bioavailability. Biopharm Drug Dispos. 2008 Sep;29(6):335-48.
  2. Otake M1, Sakurai K1, Watanabe M1, Mori C1,2.Association Between Serum Folate Levels and Caffeinated Beverage Consumption in Pregnant Women in Chiba: The Japan Environment and Children’s Study. J Epidemiol. 2018 Oct 5;28(10):414-419. doi: 10.2188/jea.JE20170019. Epub 2018 Apr 28.


  • Stemulite

    It's kind of ironic...I drink black tea at night as a way of relaxing. According to this report, that has the potential to reduce folic acid levels. This in turn could lead to depression. Funny. To me, the only positive effect of drinking tea is in your mind. If it reduces stress and helps you relax and unwind, I say it is good for you. Direct physical effects? Negligible.

  • Jarret Morrow

    Kenneth and Stumulite, thank you both for your recent comments. Both green and black tea both have several potential health benefits. I am not suggesting that people should stop drinking either type of tea. However, pregnant women should be cautioned about the potential effects on folic acid. Additionally, many people who drink tea also take vitamins and supplements. For those who do, they should definitely not take a B-complex vitamin when they are drinking tea.

  • Spin Diva

    This is very interesting. I am a big Yerba Mate tea drinker and generally drink my tea first thing in the AM and mid afternoon or evening. Vitamins always with a meal so I'm guess I probably shouldn't worry about my folic acid levels. I have always been taught to take vitamins with meals so that the fat soluble vitamins have something to bind to. Thanks for the information, I appreciate you bringing it to the table. Certainly helps to make wiser decisions when drinking or eating anything. SpinDiva!!

  • beautifuliq

    This article was very interesting. I guess there are always bad side effects to even seemingly good things. I can't wait to see what you post next.

  • GetHealthyHQ

    I wasn't aware that green tea had any adverse effects. Your blog is full of so many interesting facts! Lisa

  • Alison Gongora

    Hey could I quote some of the insight found in this entry if I reference you with a link back to your site?

Comments are closed.

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